wernher wrote: ang cpl po ba ay universal o madaming clase for different types of landskies?
CPL(circular polarizer filter) ginagamit sya to contrast colors like green and blue (ex trees and skies) and remove reflections frm glass or water. (http://en.wikipedia.org/wiki/Photographic_filter
http://www.camerafilters.com/pages/cpl.aspx). Sa clase ng Filters yes madame depende sa effects na gusto mo makuha nanjan ang ND(neutral density), IR(Infrared), Graduated, cross screen, spot filters at iba pa. here is example photo
ND Filters
Graduated/Gradient + ND filters
IR Filter
CPL filter
Most ng mga filters ginagamit lang sya sa Wide angle lenses. specially kung mahilig ka sa landscape